Long-term outcomes in patients with single ventricle physiology Single ventricle (SV) lesions are the most challenging conditions among congenital heart defects (CHD) and affect 1 out of 3000 newborns. The management of SV lesions requires multistage palliation that culminates in the Fontan operation and its modifications. Despite its benefit to improve survival and quality of life, Fontan palliation is associated with multiple morbidities leading to premature mortality or need for transplant. Families of children with single ventricle lesions are often counseled on the poor prognosis of this condition with the premise that in case of Fontan failure, a heart transplant can be pursued. However, very little data are available to inform such counseling related to risk for premature Fontan failure and death, chances to become eligible for heart transplant listing, risk of death while waiting for transplant or even about premature transplant failure if they successfully reach the transplant point. In the absence of longitudinal registries for CHDs in the US, the answers to these questions are speculative and assessment of long-term outcomes of this vulnerable population remains incomplete. Patients with SV undergo a number of interventions aiming to provide initially a stable circulation and later a ?definite? repair. At each step, various decisions are being made that affect regulation of pulmonary flow, volume load of the systemic ventricle and duration of exposure to cyanosis. These decisions may be important for the long-term success of the overall surgical strategy and are driven mostly by patient-level factors but frequently also by center-specific preferences. We hypothesize that both patient- and center-level factors can affect the long-term success of the Fontan palliation including ability to reach and survive heart transplantation. Our project will answer these questions by leveraging the use of an existing dataset combining data from a large, US-based, clinical registry for CHDs, the Pediatric Cardiac Care Consortium (PCCC), with linkage data from the National Death Index (NDI) and the Organ Procurement and Transplantation Network (OPTN) research registries. This linkage allowed us to constitute a cohort that describes the long-term mortality and transplant status of patients with an operated CHD. The depth and size of the PCCC-NDI-OPTN dataset offer an unprecedented opportunity to link patient-level variables with estimates for success in the Fontan pathway. In addition, we can leverage center variation in the surgical strategy of SV lesions to perform long-term comparative effectiveness analysis between alternative management strategies, where professional uncertainty exists. Completion of this study will provide a realistic view of expected outcomes for SV patients and will elucidate important factors affecting long-term outcomes of patients with SV physiology. This information will not only be important for educating patients and care providers but may also lead to better selection of candidates and perhaps modifications in management strategies.